qemu: needs zlib

Build error message is:
  Error: zlib check failed
  Make sure to have the zlib libs and headers installed.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/qemu/qemu.mk

@@ -8,7 +8,7 @@ QEMU_VERSION = 1.2.0
 QEMU_SOURCE = qemu-$(QEMU_VERSION).tar.bz2
 QEMU_SITE = http://wiki.qemu.org/download
 
-QEMU_DEPENDENCIES = host-pkgconf
+QEMU_DEPENDENCIES = host-pkgconf zlib
 
 #       BR ARCH         qemu
 #       -------         ----